Thu, 21 Aug 2008 01:16:43 BST CiteULike: j-ito's Schroeder http://www.citeulike.org/user/j-ito/author/Schroeder CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/j-ito/article/2647614 <i>Science (New York, N.Y.), Vol. 320, No. 5872. (4 April 2008), pp. 110-113.</i><br /><br />Whereas gamma-band neuronal oscillations clearly appear integral to visual attention, the role of lower-frequency oscillations is still being debated. Mounting evidence indicates that a key functional property of these oscillations is the rhythmic shifting of excitability in local neuronal ensembles. Here, we show that when attended stimuli are in a rhythmic stream, delta-band oscillations in the primary visual cortex entrain to the rhythm of the stream, resulting in increased response gain for task-relevant events and decreased reaction times. Because of hierarchical cross-frequency coupling, delta phase also determines momentary power in higher-frequency activity. These instrumental functions of low-frequency oscillations support a conceptual framework that integrates numerous earlier findings. Entrainment of neuronal oscillations as a mechanism of attentional selection. P Lakatos G Karmos AD Mehta I Ulbert CE Schroeder doi:10.1126/science.1154735 Science (New York, N.Y.), Vol. 320, No. 5872. (4 April 2008), pp. 110-113. 2008-04-10T01:01:54-00:00 2008 Science (New York, N.Y.) 1095-9203 320 5872 110 113 gamma lfp oscillation theta vision http://www.citeulike.org/user/j-ito/article/1292898 <i>Cereb Cortex (10 May 2007)</i><br /><br />Primates actively examine the visual world by rapidly shifting gaze (fixation) over the elements in a scene. Despite this fact, we typically study vision by presenting stimuli with gaze held constant. To better understand the dynamics of natural vision, we examined how the onset of visual fixation affects ongoing neuronal activity in the absence of visual stimulation. We used multiunit activity and current source density measurements to index neuronal firing patterns and underlying synaptic processes in macaque V1. Initial averaging of neural activity synchronized to the onset of fixation suggested that a brief period of cortical excitation follows each fixation. Subsequent single-trial analyses revealed that 1) neuronal oscillation phase transits from random to a highly organized state just after the fixation onset, 2) this phase concentration is accompanied by increased spectral power in several frequency bands, and 3) visual response amplitude is enhanced at the specific oscillatory phase associated with fixation. We hypothesize that nonvisual inputs are used by the brain to increase cortical excitability at fixation onset, thus "priming" the system for new visual inputs generated at fixation. Despite remaining mechanistic questions, it appears that analysis of fixation-related responses may be useful in studying natural vision. Transient Cortical Excitation at the Onset of Visual Fixation. Csaba Rajkai Peter Lakatos Chi-Ming Chen Zsuzsa Pincze Gyorgy Karmos Charles E Schroeder Cereb Cortex (10 May 2007) 2007-05-13T21:38:43-00:00 2007 Cereb Cortex 1047-3211 eye-movement gamma lfp oscillation vision